If the first statement of a module, class, or function definition is a string, that string becomes a documentation string for the associated object, as in the following example:
def fact(n): "This function computes a factorial" if (n <= 1): return 1 else: return n*fact(n-1)
Code-browsing and documentation-generation tools sometimes use documentation strings. The strings are accessible in the __doc__ attribute of an object, as shown here:
>>> print fact.__doc__ This function computes a factorial >>>
The indentation of the documentation string must be consistent with all the other statements in a definition.